Web support assembly

ABSTRACT

A web support assembly for a moving web of substrate material includes a base having a primary support arm pivotally mounted thereto so as to be displaceable from a first position to a second position. The web support assembly includes a first biasing member in mechanical communication with the primary support arm. The first biasing member operates to impart a first biasing force to the primary support arm so as to move it from its first position to its second position. The system includes a dancer arm which is pivotally mounted to the primary support arm so as to be displaceable from a first position to a second position relative primary support arm. The web support assembly further includes a second biasing member in mechanical communication with the dancer arm. The second biasing member operates to impart a second biasing force to the dancer arm so as to move it from its first position to its second position. A roller is rotatably supported on the dancer arm. The roller is configured to engage a portion of the web. The web support assembly operates to maintain continuous contact between the roller and the moving web of substrate material as it passes through a multi-station processing system.

FIELD OF THE INVENTION

This invention relates, generally, to assemblies for supporting andguiding a moving web of substrate material. More specifically theinvention relates to assemblies for supporting an end portion of avertically disposed, elongated web of substrate material as it movesthrough a multi-station processing system. In particular the inventionrelates to an assembly for supporting and guiding a vertically disposedweb of substrate material in a system for the continuous production ofphotovoltaic devices.

BACKGROUND OF THE INVENTION

Systems and methods have been developed for the high volume fabricationof photovoltaic devices. In such processes, one or more webs ofsubstrate material, typically stainless steel, are continuously fed froma payout chamber through a plurality of deposition stations in whichlayers of semiconductor material are sequentially deposited onto thewebs. The coated webs are then wound onto rolls in a take-up chamber andremoved for subsequent processing into photovoltaic modules. Inparticular systems of this type, the web or webs of substrate materialare maintained in a vertical orientation as they pass through thedeposition apparatus. Some systems of this type are shown, for example,in U.S. Pat. No. 4,423,701 and in published U.S. patent application2004/0040506, which are incorporated herein by reference.

Web transport and guidance are critical parameters in deposition systemsof this type. In order to assure deposition of high qualitysemiconductor layers, precise tolerances must be maintained between themoving substrate web and active components of the deposition system.Likewise, the moving web must travel along a precise path through thevarious chambers so as to avoid binding, twisting or other deformationswhich could compromise the integrity of the substrate web or thedeposition system. All of these problems are complicated by the factthat deposition systems of this type frequently have about 300 foot ormore lengths of substrate web actively moving therethrough at any time,and a typical substrate material has a weight of approximately ¼ poundper linear foot. The relatively heavy, relatively long substrate cancause problems of sagging and twisting since gravity tends to urge thesubstrate into a catenary configuration, and these problems can beenhanced by web geometry variation and differential thermal expansion ofthe web in the apparatus.

In apparatus of this type, transport systems for the substrate web mustalso be designed so as to avoid making contact with semiconductormaterial deposited on the active face of the substrate web, since suchcontact could degrade the operational performance of the semiconductordevice. And finally, substrate transport systems must also be designedso as to avoid bending, burring or other deformation of the substrateweb, since such damage will prevent the coated substrate material frombeing wound into a uniform roll. This factor is critical since any suchnon-uniformity in the roll can damage the sensitive semiconductor layersduring subsequent processing. In one prior art approach as is disclosedin published U.S. patent application 2006/0278163 a substrate supportsystem incorporates a magnetic guidance assembly and a number of supportrollers to transport vertically oriented webs through a depositionsystem.

The rollers of the system in the '163 patent application guide anddirect edges of the moving web. However, in the operation of systems ofthis type it has been found that problems can arise because ofirregularities in the web material itself as a result of geometricvariations in the manufacture of the web and/or deformations resultantfrom differential thermal expansion. As a result of such variations, theamount of force exerted by the moving substrate web on any one rollermay vary as the web moves therethrough. Excessive force between theroller and the web can deform the edge of the web creating a burr,buckle or bend. Decreased force between the roller and the web can alsobe a problem, particularly if the web moves away from the roller since,under the high vacuum, relatively high temperature conditionsencountered in the deposition chamber, cold welding of the substrate androller can occur when contact is reestablished causing damage to the weband/or the roller. Therefore, there is a need for a web support systemwhich can operate to reliably and precisely move relatively heavy, longwebs of substrate material through a multistage high vacuum depositionsystem of the type used for the manufacture of photovoltaic devices andother semiconductor devices. Any such system should be relatively simpleand reliable in its operation and should be compatible with high vacuum,ultra clean conditions and should not introduce contamination into thesystem.

As will be explained in detail hereinbelow, the present inventionprovides a web transport system which can be incorporated intomulti-station processing systems, for example, high volume systems forthe continuous preparation of photovoltaic and other semiconductordevices. These and other aspects and advantages of the present inventionwill be apparent from the drawings, discussion and description whichfollow.

SUMMARY OF THE INVENTION

The present invention comprises a web support assembly for a moving andguiding web of material. In a specific instance, the web supportassembly includes a base, a primary support arm which is pivotallymounted to the base so as to be displaceable from a first position to asecond position relative to the base, and a first biasing member whichis in mechanical communication with the primary support arm. The firstbiasing member is operable to impart a first biasing force to theprimary support arm so as to move it from its first position to itssecond position. The web support assembly further includes a dancer armwhich is pivotally mounted on the primary support arm so as to bedisplaceable from a first position to a second position relative to theprimary support arm. A second biasing member is in mechanicalcommunication with the dancer arm. The second biasing member is operableto impart a second biasing force to the dancer arm so as to move it fromits first position to its second position. The web support assemblyfurtier includes a web support roller which is rotatably supported bythe dancer arm. The roller is configured to engage a portion of the web.In specific instances, the first biasing force is greater than thesecond biasing force. In particular instances, the biasing members maybe springs, elastomeric bodies, pneumatic cylinders, magnetic devices,hydraulic cylinders, and various combinations of the foregoing.

In a specific instance, the first biasing member is a spring whichextends between a primary support arm and the base. In some instances,the second biasing member may be a spring which extends between thedancer arm and the primary support arm.

In specific instances, the web support roller includes a groove which isconfigured to engage a web, and this groove may, in particularinstances, be an asymmetric groove. In some instances, the asymmetricgroove may be configured so that the two faces of the groove form a 90degree angle. In specific instances, the groove is configured so that anend surface of the substrate does not contact the base of the groove.

Further disclosed is an apparatus for the continuous deposition of alayer of semiconductor material onto an elongated web of substratematerial which is advanced therethrough, wherein the apparatus includesthe web support assembly of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a web support assembly of the presentinvention;

FIG. 2 is a perspective view of the web support assembly of FIG. 1showing a web of substrate material engaged therewith;

FIG. 3 is perspective view of a primary support arm and a dancer arm ofthe web support assembly of FIG. 1;

FIG. 4 is an illustration of the web support assembly of FIG. 1 in adown position wherein a high substrate load is imposed thereupon;

FIG. 5 is a depiction of the web support assembly of FIG. 1 in an upposition wherein a low level of contact force is imposed on thesubstrate; and

FIG. 6 is a cross-sectional view of a portion of a roller of the presentinvention as engaged with a web of substrate material.

DETAILED DESCRIPTION OF THE INVENTION

The present invention comprises a web transport system which includes anumber of web support assemblies which may be utilized to support andguide a substrate material through a processing system. In that regard,the invention will have utility in a large number of systems whereintransportation of a web of material is an aspect of the processingsystem. The present invention will be described with regard to aspecific utility wherein it is employed to guide and support a substrateweb in a system for the high volume deposition of photovoltaicsemiconductor material in a continuous roll-to-roll process.

The web support assemblies of the present invention are configured so asto maintain a portion of the web support in continuous contact with anedge of the substrate despite fluctuations in substrate width and/orposition. Furthermore, the web support assembly is configured so thatexcessive force between the edge of the substrate web and the contactedsupport is minimized. In exemplary embodiments, the web support assemblyincludes a multi-biasing arrangement configured to bias the substrateweb between a first position and a second position. In an exemplaryembodiment, the multi-biasing arrangement includes a biasing forcetransition zone with a discontinuous contact force at a web/supportcontact location. In an exemplary embodiment, a portion of the web incontact with the web support has a deflection that is substantially zerowithin the biasing force transition zone. In exemplary embodiments, theweb support assembly biases the web with a greater biasing force along afirst direction compared to a biasing force exerted upon the web along asecond direction.

The system of the present invention may be implemented in a number ofembodiments. One specific embodiment as particularly adapted for use inan apparatus for the fabrication of photovoltaic devices will be shownherein. In some embodiments, a first plurality of web support assemblieswill be utilized to support/guide a first edge of a substrate web, whileone or more web support assemblies are used to support/guide a secondedge of the substrate web. In certain embodiments, a portion of theplurality of web support assemblies will be configured different fromthe other web support assemblies along the first and/or second edges ofthe web, for example, in terms of structural configuration,load/temperature capability, materials, etc. However, it is to beunderstood that other embodiments of the invention may be implemented,and likewise, the systems and apparatus of the present invention may beincorporated into systems utilized for the manufacture of a variety ofmaterials. It is to be further understood that the Figures of thisapplication are not drawn to scale, rather the Figures are drawn toillustrate most clearly the principles of this disclosure discussedherein.

Referring now to FIGS. 1 and 2, there is shown a web support assembly10, configured in accord with an embodiment of the present invention.The web support assembly 10 includes a base portion 12 which functionsto support the remainder of the assembly and further functions to allowthe assembly to be mounted to other structure. The base 12, as well asother portions of the web support assembly, can be fabricated frommaterials that withstand loads applied thereto and that do not degradeprocesses of the system. For example, it would not be desirable where amaterial of the web support assembly releases gases or other contaminatethat degrades the integrity of a semiconductor deposition process. Incertain embodiments, the assembly materials include aluminum, mild orhigh-strength steel, stainless steel, a high strength plastic, andcombinations thereof. In the present embodiment unless otherwise notedherein, the majority of the assembly components are made from aluminum.A primary support arm 14 is pivotally mounted to the base 12 by a pivotjoint 16 which allows the primary support arm 14 to be movable from afirst position to a second position, relative to the base.

The web support assembly also includes a biasing member, in thisinstance a coil spring 18 which is mounted between the base 12 and theprimary support arm 14. The coil spring 18 operates to exert a biasingforce which tends to move the primary support arm from a first positionto a second position. In many embodiments, the spring 18 will bepreloaded a predetermined amount, for example, to urge the primarysupport arm upward as shown in FIG. 1 (e.g. second position), to suit aconfiguration of web (e.g. geometry and weight) and web movementparameters in the processing system. While the biasing in the FIG. 1embodiment is accomplished by the coil spring 18, other biasing memberssuch as elastomeric bodies of material such as synthetic or naturalrubber may be used to provide the biasing force. Yet other biasingmechanisms known in the art such as gas filled pneumatic cylinders,hydraulic cylinders, counterweights, magnetic devices (includingelectromagnetic devices) and the like may also be used as biasingmembers. Also, while the spring 18 is shown as being in a particularlocation between the base 12 and support arm 14, it will be appreciatedthat it could be otherwise disposed. For example, the biasing may beaccomplished by a coil spring associated with the pivot 16.Alternatively, the biasing member need not be in any mechanicalcommunication with the base. For example, biasing may be accomplished bya spring or elastomeric body extending between the primary support arm14 and some other portion of the apparatus in which the system isdisposed.

The web support assembly 10 of FIGS. 1-3 further includes a dancer arm20 which is pivotally supported on the primary support arm 14, in thisinstance Through a pivot joint 22. A second coil spring 24 is disposedbetween the dancer arm 20 and primary support arm 14 and it operates tobias the dancer arm 20 between a first and second position relative tothe primary support arm 14. As discussed with regard to the first spring18, the second spring 24 may be otherwise disposed; or, it may compriseanother type of biasing member such as an elastomeric body, pneumaticcylinder, hydraulic cylinder, counterweights, magnetic device or thelike. Rotatably affixed to the dancer arm 20 (at hole 28 shown in FIG.3) is a support roller 26, which operates to engage an edge of a web ofsubstrate material, and as such it may be grooved or otherwiseconfigured to aid in its retention of the web. In this embodiment, thesupport roller is primarily made of substantially non-magnetic, 304stainless steel. In an alternative embodiment, the support roller caninclude a ceramic material that contacts the web.

Referring now to FIG. 2, there is shown a perspective view of the websupport assembly 10 of FIG. 1 with a portion of a web of substratematerial 30 engaged therewith. It is to be understood that in a typicalapplication the substrate material 30 comprises an elongated web ofmaterial; however, for purposes of simplification, only a portion of theweb is shown in FIG. 2. Additionally, the embodiment of web supportassembly shown in FIG. 2 is configured so two webs can be independentlyguided/supported, wherein each roller supports/guides a web moving overthe roller independent from the other web-roller interaction, Forclarity purposes only one web is shown in phantom outline in FIG. 2, Itis to be understood that even though only one side (one web support) ofFIG. 2 has reference numerals and the same side is shown other Figures,the principles discussed herein with respect to the parts denoted byreference numerals apply to the other web support without referencenumerals in FIG. 2.

In the FIG. 2 illustration, the support roller 26 has engaged the edgeof the vertically disposed substrate 30, and as will be seen, a groove27 in the roller facilitates retention of the substrate 30. Referring toFIG. 4, the weight of the substrate 30 bearing onto the roller 26 hascompressed the second coil spring (24 shown in FIG. 1) between thedancer arm 20 and primary support arm 14. The biasing force of thesecond spring has, in this embodiment, been selected so as to be lessthan the biasing force of the first spring 18 and sufficient to overcomethe weight of the dancer arm and roller. In the FIG. 2 configuration thefirst spring 18 is supporting the primary arm 14, the dancer arm 20 andthe roller 26 against the downwardly exerted force of the substrate 30.If that force increases because of distortions of the substrate web orthe like, the spring 18 will absorb further downward force preventingdamage to the web while maintaining good contact with the web.Distortions of the substrate web can be caused, in non-limitingexamples, from web geometry variations, thermal and dynamic loads, etc.For example, if a portion of the bottom surface/edge of the substrateweb being supported by the roller is disposed below a theoretical passline of the web, the web will tend to exert a contact force upon theroller to move the roller toward a position shown in FIG. 4. Here thetheoretical pass line is a line of travel of the bottom surface/edge ofthe web if it was perfectly straight, or the web bottom surface passline has no distortions from that line due to part/web geometryvariation, thermal and dynamic loads, movement parameters, etc. In thisembodiment, the first spring is configured so a threshold predeterminedcontact force between the roller and the web is not exceeded. Thethreshold contact force can be based on deformation, web/rollerdeflection, material yield, etc. In this embodiment, the thresholdcontact force is based on a predetermined force that will not deform theweb, e.g. dent, crease etc., beyond a predetermined amount when the webis disposed below the pass line.

In that regard, FIG. 4 shows a side elevation view of the assembly 10 ina downwardly biased position. In the event that the web downward forcedecreases, the spring 18 will bias the primary support arm 14, theassociated dancer arm 20 and roller 26 back toward a neutral position.Should the web downward force still decrease, as would be the case ifthe web were moving so as to lift from the roller, e.g. when the bottomsurface of the web moves above the theoretical pass line, the spring 18will drive the primary support arm 14 to its full extent of travel as isshown in FIGS. 2, 3, 5; and at that point, the second spring 24 willoperate to lift the dancer arm 20 so as to further raise the supportroller 26 and thereby maintain contact with the edge of the web. Asnoted above, the biasing force of the second spring 24 is generally lessthan that of the first spring 18. Therefore, the pressure exerted by theroller onto the web will be less than it would be in a full downwardcontact position; but such pressure will be sufficient to maintain thetwo in contact and prevent the web from leaving the roller. The biasingforces of the springs can be selected based upon specifics of aprocessing system and a substrate web as will be discussed hereinbelow.In this embodiment, the first and second springs are configured toprovide a discontinuous transition of contact force between the rollerand web when the roller is in a force transition zone between the rollerpositions of FIGS. 4 and 5. Within that transition zone there is aposition where the vertical displacement of the roller is substantiallyzero and the force between the web and roller either increases ordecreases depending on the whether the web is moving toward a directionbelow or above the pass line. In the embodiment described hereinabove,the web support can be considered to bias the substrate web between aposition below the theoretical pass line, similar to that shown in FIG.4, and another position above the pass line, similar to that shown inFIG. 5.

The rollers used to contact and support/guide the web may be variouslyconfigured. In this embodiment, the roller includes a groove or someother feature for maintaining the substrate and roller in engagement.Referring now to FIG. 6, there is shown a portion of a roller 26 of thepresent invention having a web of substrate material 30 engaged with agroove 27 therein as shown in FIG. 2. In the FIG. 6 embodiment thegroove is an asymmetric groove. That is to say, the two faces of thegroove have different angles of contact with the substrate 30. Thegroove has a first face 32 which contacts an edge of a first face orsurface of the substrate 30 at a first angle A, which in someembodiments is in the range of 5 degrees to 45 degrees. The grooveincludes a second face 34 which contacts an edge of a second face orsurface of the substrate 30 at a second angle B which in someembodiments is in the range of 5 degrees to 30 degrees. In particularinstances, angle B is greater than the angle A. Furthermore, in thisembodiment, angle A and angle B are complementary angles; that is tosay, they add up to 90 degrees. In specific instances, the system isconfigured so that the deposition of the semiconductor material takesplace on the face of the substrate 30, which defines angle A. Otherangular relationships and orientations may be implemented. It will alsobe seen that in the FIG. 6 illustration the face or the end surface ofthe substrate web 30 does not contact the base of the groove. Contactbetween the roller 26 and the web 30 is established by a pinch betweenthe faces 32, 34 of the roller and the edges or corners of the web. Ithas been found that this type of contact provides desirable websupport/guidance and further prevents damage to the face or end surfaceof the substrate web.

In systems for the deposition of semiconductor material onto a movingsubstrate web wherein the semiconductor deposition takes place on theface of the web closest to roller face 32, very good results are foundutilizing the geometric relationships of FIG. 6. In this regard, aroller configured as per FIG. 6 is very effective in maintaining thesubstrate 30 in a precise alignment with a deposition station whileavoiding damage to the substrate.

In view of the foregoing, various support assemblies may be readilyconfigured by those of skill in the art. The precise dimensions andcharacteristics of the assembly will depend upon particularapplications. As discussed above, a typical high volume continuousprocess apparatus for the deposition of semiconductor material mayemploy stainless steel substrate material having a weight ofapproximately ¼ pound per linear foot. In one system of this type, thesubstrate material is supplied in coils of approximately 8000 feet inlength, and at any one given time approximately 279 feet of thesubstrate web is actively moving through the deposition system. And asis further noted, such systems may include up to 6 webs movingtherethrough in a substantially parallel relationship. In thisconfiguration, each web has 60 supports associated therewith. Therefore,each roller will be supporting approximately 1.16 pounds on the average.In a system of this type, the primary spring (18 hereinabove) willtypically be preloaded to a level of approximately 2.5 to 3.5 pounds andthe dancer spring (24 hereinabove) will be selected so that a load of0.75 to 1 pound will compress it to its fully down position, as shown inFIG. 4. In instances where differently configured systems and/orsubstrate webs are employed, the biasing force of the springs or otherbiasing members may be adjusted accordingly.

The web support assembly of the present invention has been describedwith regard to its use to support and guide the bottom edge of avertically disposed substrate. However, assemblies of this type may alsobe disposed to engage a top edge of a vertically disposed substrate. Insuch instances, the biasing forces may be adjusted accordingly. Also,the support assembly has been described with regard to its use inconjunction with steel substrates. It is to be understood that suchassemblies may be used to support and guide other types of substratewebs, including polymeric substrates, composite substrates, fibroussubstrates and the like.

In view of the teaching presented herein, other modifications,variations and embodiments of this invention will be apparent to thoseof skill in the art. All of such embodiments are within the scope ofthis invention. The foregoing drawings, discussion and description areillustrative of specific embodiments of the invention, but are not meantto be limitations upon the practice thereof. It is the following claims,including all equivalents, which define the scope of the invention.

1. A web support assembly for a moving web of material, said web supportassembly comprising: a base; a primary support arm which is pivotallymounted on the base so as to be displaceable from a first position to asecond position relative thereto; a first biasing member in mechanicalcommunication with said primary support arm, said first biasing memberbeing operable to impart a first biasing force to said primary supportarm so as to move said primary support arm from its first position toits second position; a dancer arm which is pivotally mounted on saidprimary support arm so as to be displaceable from a first position to asecond position relative to said primary support arm; a second biasingmember in mechanical communication with said dancer arm, said secondbiasing member being operable to impart a second biasing force to saiddancer arm so as to move said dancer arm from its first position to itssecond position; and a web support roller rotatably supported by saiddancer arm, said roller being configured to engage a portion of saidweb.
 2. The web support assembly of claim 1, wherein said first biasingforce is greater than said second biasing force.
 3. The support of claim1, wherein said first biasing member and said second biasing member areselected from the group consisting of: springs, elastomers, pneumaticcylinders, hydraulic cylinders, magnetic devices, and combinationsthereof.
 4. The support of claim 1, wherein said first biasing member isa spring which extends between said primary support arm and said base.5. The support of claim 1, wherein said second biasing member is aspring which extends between said dancer arm and said primary supportarm.
 6. The support of claim 1, wherein said web support roller includesa groove which is configured to engage an edge of the web.
 7. Thesupport of claim 6, wherein said groove is an asymmetric groove.
 8. Thesupport of claim 6, wherein said groove includes a first face and asecond face, and wherein said first face and said second face form a 90degree angle.
 9. The support of claim 6, wherein said groove isconfigured so that said groove includes a first face and a second face,and wherein said faces establish a pinch contact with said substrate sothat an end surface of said substrate does not contact the bottom ofsaid groove.
 10. The support of claim 6, wherein said roller isconfigured so that when the substrate material is disposed within thegroove, a first face of said groove forms a first angle A, with a firstface of said web, and a second face of said groove forms a second angleB with a second face of said web, and wherein angle A and angle B aredifferent.
 11. The web support assembly of claim 10, wherein angle A andangle B are complementary.
 12. An apparatus for the continuousdeposition of a semiconductor material onto an elongated web ofsubstrate material which is advanced therethrough, said apparatusincluding the web support assembly of claim
 1. 13. The web supportassembly of claim 1, further comprising a second web support assemblyconfigured to support a second moving web, said first and second webs ina spaced, substantially parallel relationship.
 14. The web supportassembly of claim 13, wherein the web support roller of the web supportassembly is configured to support/guide the web independent of theinteraction between the second web support assembly and the second web.15. The web support assembly of claim 13, wherein the web support andthe second web support assemblies are joined to a common base.
 16. A websupport assembly for supporting/guiding a substrate web comprising amulti-biasing arrangement configured so a surface of the web is biasedalong a first direction with a first bias force and the surface of theweb is biased along a second direction with a second bias force, thesecond direction being substantially opposite the first direction. 17.The web support assembly of claim 16, wherein the multi-biasingarrangement is configured to have a biasing force transition zonebetween a web first position and a web second position where the web hasa deflection within the biasing force transition zone that issubstantially zero.
 18. The web support assembly of claim 16, whereinthe multi-biasing arrangement biases the surface of the web with agreater force along the first direction compared to a biasing forceexerted upon the web along the second direction.
 19. The web supportassembly of claim 18, further comprising a roller, wherein the firstbias force along the first direction reacts web movement into tieroller, and the second bias force along the second direction acts tomaintain contact between the roller and web as the web moves away fromthe roller.
 20. The web support assembly of claim 16, wherein thebiasing arrangement includes a coil spring.